x3p_crosscut_optimize: Identify a reliable cross section

In heike/bulletxtrctr: Automatic Matching of Bullet Striae

Identify a reliable cross section

Description

Identifies a "representative" cross section for a bullet land engraved area. Striation marks on a bullet land are best expressed at the heel (bottom) of a bullet where break-off is still problematic. Using cross-correlation we identify a cross section that is the closest to the bottom of the bullet but does not suffer from break-off. If the resulting cross section is equal to the maximum of the search area (defined in xlimits), there should be some investigation to determine whether this cross section is usable, due to the risk of tank rash. TODO: are missing values only on the right hand side (leading shoulder)?

Usage

x3p_crosscut_optimize(
  x3p,
  distance = 25,
  ylimits = c(50, NA),
  minccf = 0.9,
  span = 0.03,
  percent_missing = 50
)

Arguments

x3p	if character, path to an x3p file. Otherwise a scan in x3p format is expected. The assumption is that the scan is taken across the bullet land, with an upright bullet, i.e. heel along x with y = 0. (0,0) defines the bottom left corner of the scan.
distance	positive numeric value indicating the distance between cross sections to use for a comparison
ylimits	vector of values between which to check for cross sections in a stable region. In case the upper limit is not specified explicitly, it is determined by the scan itself.
minccf	minimal value of cross correlation to indicate a stable region
span	The span for the loess smooth function
percent_missing	maximum percent missing values allowed on the crosscut to be picked

Value

dataframe of crosscut

Examples

## Not run: 
# Set the data up to be read in, cleaned, etc.
library(bulletxtrctr)
library(x3ptools)
library(ggplot2)

example_data <- bullet_pipeline(
  location = list(Bullet1 = c(hamby252demo$bullet1[3])),
  stop_at_step = "clean",
  x3p_clean = function(x) x %>%
      x3p_scale_unit(scale_by=10^6) %>%
      rotate_x3p(angle = -90) %>%
      y_flip_x3p()
)

x3p_crosscut_optimize(example_data$x3p[[1]])
x3p_crosscut(example_data$x3p[[1]], 75) %>%
  ggplot(aes(x = x, y = value)) + geom_line()

## End(Not run)

heike/bulletxtrctr documentation built on March 8, 2024, 7:41 p.m.